重金属污染水体背景下的底质反射率光谱特征及其对离水反射率贡献影响分析

doi:10.3964/j.issn.1000-0593(2024)01-0111-07

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摘要：水体重金属遥感反演是水环境遥感领域中的难题，目前仍有相当多的基础性问题有待解决，而浅水区底质对离水反射率贡献规律是将来遥感反演模型精度其中一个重要影响因素，尤其在重金属污染这种特殊的背景下，揭示其贡献规律对提升水体重金属遥感模型精度有重要作用，测量结果对研究重金属尾矿底泥的反射率光谱特征以及区分常见水底底质有参考意义。首先利用光谱仪测量获得广东大宝山尾矿底质反射率，发现其在波长755、1 280、1 620和2 200 nm存在反射峰，有明显光谱特征，并与河床常见的粗沙、淤泥和石头三类底质反射率进行了对比分析，结果表明：一方面，粗沙和淤泥反射率呈一缓慢上升的曲线，与存在多个特征反射峰的矿区底泥有明显区别；另一方面，石头反射率则在波长范围550~650 nm出现一个宽而扁平的反射峰后随即在波长675 nm处出现波谷然后增大至波长750 nm后趋于平缓，其特征波长与矿区底泥均不一样。上述特征波长可作为重金属污染背景下底泥光谱的重要区分波段。测量水深为1 cm、10 cm和深水区的离水反射率，结合水质遥感模型计算出1 cm水深情况下底质反射光、水体散射光，并将其对离水反射率贡献进行讨论。离水反射率测量结果表明，底质对浅水区影响极大，随着水深变浅，离水反射率总体不断被抬升。而水底反射光和水体散射光对离水反射率贡献规律则以波长515 nm为分界线，向短波方向以水体散射光贡献为主，向长波方向则以水底反射光为主，贡献量由底质反射能力和水体散射能力共同决定。对考虑了底质反射光后的遥感模型精度进行评价，模型计算得到波长范围350~950 nm内的离水反射率与野外测量值对比结果，二者具有显著的线性相关（R²=0.964 2），相对误差在波长范围560~830 nm低于10%，甚者可低于5%，模型总体模拟精度较好，远比在不考虑底质影响时精度高，模型满足将来水中重金属遥感反演要求。研究结果对今后水体重金属遥感反演时处理底质影响提供了重要的参考数据和理论依据，有助推动该领域进一步发展。

关键词：水体重金属遥感；重金属矿区；底质反射率；光谱特征分析；模型精度评价

Abstract：Inversion of heavy metals in water by remote sensing is a difficult problem in remote sensing of the water environment. There are still quite a few fundamental problems to be solved. The contribution law of the bottom sediment in the shallow water area to the water-leaving reflectance is one of the important factors affecting the accuracy of the remote sensing inversion model in the future. Especially in the special background of heavy metal pollution, revealing its contribution rule plays an important role in improving the accuracy of the water heavy metal remote sensing model. Meanwhile, the measurement results have reference significance for studying the reflectance spectral characteristics of heavy metal tailings sediments and distinguishing common bottom sediments. Firstly, the reflectance of the Dabaoshan Mountain tailings bottom in Guangdong was obtained by spectrometer measurement. It has reflection peaks at wavelengths of 755, 1 280, 1 620 and 2 200 nm, and has obvious spectral characteristics. The reflectance of three types of sediments coarse sand, silt and stones, which are common in riverbeds, were compared and analyzed. The results show that, on the one hand, the reflectance of coarse sand and silt shows a slowly rising curve, which is different from the sediment in the mining area with multiple characteristic reflection peaks. On the other hand, the reflectance of the stone shows a broad but flat reflection peak in the wavelength range of 550~650 nm, then a trough at the wavelength of 675 nm, and then increases to a wavelength of 750 nm and then tends to be flat. Its characteristic wavelength is different from that of the sediment in the mining area. Therefore, the above characteristic wavelengths can be used as important distinguishing bands of sediment spectra in the background of heavy metal pollution. Then, measure the water-leaving reflectance water depths of 1, 10 cm and deep water. The water-scattered light and water-bottom reflected light were calculated at a water depth of 1 cm, and the contribution of the water-leaving reflectance was discussed. The measurement results of the water-leaving reflectance show that the sediment greatly influences the shallow water area. The contribution law of the water-scattered light and water-bottom reflected light to the water-leaving reflectance takes the wavelength of 515 nm as the dividing line: in the short-wave direction, the water-scattered light is the main contribution, while in the long-wave direction, change to the water bottom reflected light. The contribution is determined by the sediment's reflection ability and the water body's scattering ability. Finally, the accuracy of the remote sensing model after considering the water-bottom reflected light is evaluated. The comparison results of the water-leaving reflectance in the wavelength range of 350~950 nm calculated by the model and the measured value in the field show a significant linear correlation (R²=0.964 2). The relative error is less than 10% in the wavelength range of 560~830 nm and even less than 5% in some of them. The simulation accuracy of the model is good, which is far higher than that when the influence of the sediment is not considered. The model satisfies the requirements of remote sensing inversion of heavy metals in water in the future. The above research results provide important reference data and theoretical basis for processing sediment effects in remote sensing of water heavy metals inversion in the future, which will help promote further development in this field.

Key words：Remote sensing of heavy metals in water;Heavy metal mining area;Sediment reflectance;Spectral characteristic analysis;Model accuracy evaluation

收稿日期: 2022-06-28 修订日期: 2022-10-15

中图分类号:

O657.3

基金资助: 国家自然科学基金项目（41901352），广东省自然科学基金项目（2020A1515010780），广州市科技计划项目（202102020454），浙江省生态环境科研和成果推广项目（2020HT0010）资助

通讯作者: 邓孺孺 E-mail: eesdrr@mail.sysu.edu.cn

作者简介: 梁业恒，1987年生，中山大学地理科学与规划学院副研究员 e-mail: liangyeheng@163.com

引用本文:

梁业恒，邓孺孺，梁钰婕，刘永明，吴仪，袁宇恒，艾先俊. 重金属污染水体背景下的底质反射率光谱特征及其对离水反射率贡献影响分析[J]. 光谱学与光谱分析, 2024, 44(01): 111-117.
LIANG Ye-heng, DENG Ru-ru, LIANG Yu-jie, LIU Yong-ming, WU Yi, YUAN Yu-heng, AI Xian-jun. Spectral Characteristics of Sediment Reflectance Under the Background of Heavy Metal Polluted Water and Analysis of Its Contribution to Water-Leaving Reflectance. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2024, 44(01): 111-117.

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